vpu: encoder: Fix get_property values

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
vpu: encoder: make sure an enabled nForceIPicture flag stays enabled

Without this, nForceIPicture might be set to 0 even if it was 1 before,
due to the idr_interval

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>
vpu: encoder: add configs for bitrate and intra refresh in set_format()

Signed-off-by: Carlos Rafael Giani <dv@pseudoterminal.org>